1. Field of Invention
The present invention relates generally to converting crystalline wax, as, for example, exists in slop oil, to an amorphous form of wax, causing it to be dissolvable in, for example, crude oil at, for example, ambient temperature and maintained in a dissolved state for a prolonged period of time at ambient temperature, and more particularly, in its preferred, exemplary embodiment, to the use preferably of a chemical composition of surfactants, polymeric dispersants and corrosion & scale formation inhibitors that can, for example, recover waste hydrocarbon products (paraffin waxes, asphaltenes, and coke) from both naturally-occurring and synthetic sources, and more particularly to recover these waste hydrocarbon products for use as energy sources and to reduce environmental pollution. A number of other applications is also disclosed and claimed.
Also, since the advent of new environmental laws for the disposal of hydrocarbon based sludge, the petrochemical industries have implemented the use of various types of cleanup systems. The most commonly used methods have been mechanical systems such as centrifuges, decanters, tricanters and various types and designs of liquid-solid separators. Most mechanical separation systems are limited by temperature and volume constraints.
Using mechanical systems alone, solid-liquid separations are never complete. In order to obtain a complete separation with a minimum of residual emulsion rag (BS&W) remaining, chemicals are added to enhance the efficiency of the separation. Since refinery and petrochemical sludge oil residues are listed by the E.P.A. as toxic and hazardous wastes, they must be disposed of at a regulated special waste dump. Because of the limited amount of sites available for disposing such toxic and hazardous wastes, the disposal costs are extremely high.
In the year 2000 the average worldwide cost for disposal of these wastes ranged from 350 to 500 dollars/metric ton (52 to 75 dollars per barrel) of sludge oil waste. Oilfield production slop oil and sludge wastes are also a problem and are normally treated with the same methods used by refineries.
2. Prior Art
For general background, “prior art” information pertinent to the invention, reference is had to:                The Chemistry and Technology of Waxes by Albin H. Warth, published by Reinhold Publishing Corp. (New York, 1947), p. 239 et al;        Petroleum Refinery Engineering by W. L. Nelson, published by McGraw-Hill Book Co. (New York, 4th Ed., 1958), particularly Chapter 12 “DeWaxing” (pp. 374-75 et seq.);        Physical Chemistry by Walter J. Moore, published by Prentice-Hall, Inc. (New York, 1955), particularly Chapter 16 “Surface Chemistry” (p. 498 et seq.); and        chemical and process technology encyclopedia edited by Douglas M. Considine, published by McGraw-Hill Co. (New York, 1974), particularly its sub-section on “Waxes” (p. 1167 et seq.).        
Also some patents cited in the parent application hereof include the following—
Patent No.Inventor(s)DateJP409296162[Abstract Only]November 19976,000,412Chan et alDecember 19995,525,201Diaz-arauzo et alJune 19964,551,239Merchant et alNovember 19854,477,337Rouden et alOctober 1984
Also, the publications entitled “Cleaning Up the Slop: Part II” in Hydrocarbon Engineering (December 1999) and the preceding article “Cleaning Up the Slop” (July/August 1999) are noted, but are not considered “prior art” in view of the priority date of the parent application (U.S. Pat. No. 6,322,621) for claims which incorporate innovative aspects of the parent's technology, which are patentable either alone or in combination with the new technology of the further, second aspect of the present invention.
Waxy materials present in crude oils and in the high boiling fractions are considered to be crystalline throughout but under certain conditions may behave like a colloid. Certain wax solutions of refined products such as petrolatum, when agitated or mixed for long periods near or at the crystallizing temperature, will form a completely transparent jelly. But the same solution, when chilled rapidly with moderate agitation will precipitate a wax that can be centrifuged.
It was observed many years ago in the sweating of solid paraffins at the petroleum refinery that three crystalline forms (manifestations) of hydrocarbons are involved. These are known as “plate”, “malcrystal”, and “needle” [note, for example, The Chemistry and Technology of Waxes by Albin H. Warth, published by Reinhold Publishing Corp. (New York, 1947), p. 239]. It was recognized that the relative proportion of these types of crystals not only has a relationship to the source of the crude but also to the process of handling the wax.
The members of each series crystallize similarly as either plates, malcrystals, or needles. If one type is present (plate, mal, or needle), the crystal form remains the same regardless of such factors as the amount and kind of solvent.
When crude oil is pumped from the ground and transported through pipelines, transported by ocean tankers, or stored in storage tanks on land or offshore, a large amount of heavy material separates and comes out of solution. The main component of this residue is high molecular weight paraffin waxes. In some cases the wax represents as much as ninety (90%) percent of the deposited residues.
The amounts of wax present in crude oil are to a large extent an indicator of its origin, whether the crude originated in Venezuela, Mexico, or Malaysia.
This mixture of wax, oil, sand, and water is referred to as “slop oil,” or “slop,” in the petroleum industry. The percentage of slop oil varies according to the type of crude and the conditions under which it has been transported. Usually the amount of slop oil ranges from a low of a half percent (0.5%) to a high of ten percent (10%); normally, it is in the range of two percent (2% to 5%) to five percent.
For the last century and until today the only way to keep slop oil from separating from crude oil is to heat the slop oil while it is being transferred into mixing tanks with crude oil. The cost of keeping slop oil mixed with crude oil is a function of many variables such as temperature, solvent diluents, and residence time of the crude in a tank or pipeline.
The petroleum industry is plagued with the problem of having to deliver crude oil to refineries in a timely and economic manner. If a pipeline becomes plugged up or clogged because of paraffin wax precipitating out during the pumping operation, a crisis can arise. Numerous pipelines worldwide are clogged daily or monthly due to wax precipitating out of the crude oil. Daily, 50,000,000 barrels of crude oil are pumped from the ground worldwide (as of May, 1999). If 5% of the heavy residues come out of the crude oil being transported, whether by pipeline or tanker, the amount of slop oil or crude residue is 2,500,000 barrels per day. This amounts to 912,000,000 barrels per year. If 70% of this slop oil is useable crude which can be processed to refine production, then the amount of recoverable hydrocarbon equals over 640,000,000 barrels per year. At a cost of $10.00/barrel of crude oil this amounts to the recovery of $6.4 billion per year of useable hydrocarbon as either energy or petrochemical feedstock.
Another important factor in the transportation of crude oil is the corrosion of pipelines, storage tanks, and marine tankers. One of the main sites of corrosion in pipelines and storage tanks is at the point of buildup of the paraffin wax. At this site corrosion-causing chemicals become embedded in the wax and migrate to the metal surfaces. Pipelines with intrinsically large wax buildup or settling have many more corrosion problems than pipelines where the oil moves swiftly without deposition occurring. This results in increased maintenance cost and in some cases pipelines have to be shut down and crude must be rerouted to new lines as a result of both the clogged lines and corrosion. One of the main maintenance tools used to unclog crude oil pipelines is pigging the line. In this process a small device shaped like a pig with a series of scrapers on its sides is shot through the line to remove all the wax. This wax is then collected at traps located along the line and shipped to pipeline pumping stations for storage.
In storage tanks the problems associated with wax settling out are tremendous and present an extremely challenging task to refiners and terminal operators.
When crude oil remains idle and cold in a storage tank, a heavy residue forms that, over time, accumulates at the bottom of the tank and reduces useable tank volume. This residue, known as slop oil (or, slop), consists of heavy paraffinic waxes and asphaltenes which solidify in crystalline form. Slop oil is extremely difficult to remove from tanks and presents a very costly disposal problem for the refinery and terminal operator.
Traditional tank cleaning methods use a combination of heat (e.g., 60 to 75 degrees C. or greater) and mechanical agitation to force the slop oil back into solution with crude oil, so the mixture can be pumped out of the tank. In order to keep the waxes and asphaltenes in solution with the crude oil, the mixture must be kept at, for example, 75 degrees C. or greater and, in most cases, continuously circulated. The tremendous amounts of energy required to heat and circulate large volumes of dense crude oil to these elevated temperatures over long periods of time increase handling costs dramatically.
After pumping out the slop oil containing paraffin waxes and asphaltenes, the slop oil mixture must be kept hot or the wax will separate from solution, and the problems associated with slop oil will recur.
This need to use heat results in great energy cost and losses.
Also, as noted above, since the advent of new environmental laws for the disposal of hydrocarbon based sludge, the petrochemical industries have implemented the use of various types of cleanup systems. The most commonly used methods have been mechanical systems such as centrifuges, decanters, tricanters and various types and designs of liquid-solid separators. Most mechanical separation systems are limited by temperature and volume constraints.
Using mechanical systems alone, solid-liquid separations are never complete. In order to obtain a complete separation with a minimum of residual emulsion rag (BS&W) remaining, chemicals are added to enhance the efficiency of the separation. Since refinery and petrochemical sludge oil residues are listed by the E.P.A. as toxic and hazardous wastes, they must be disposed of at a regulated special waste dump. Because of the limited amount of sites available for disposing such toxic and hazardous wastes, the disposal costs are extremely high.
In the year 2000 the average worldwide cost for disposal of these wastes ranged from 350 to 500 dollars/metric ton (52 to 75 dollars per barrel) of sludge oil waste. Oilfield production slop oil and sludge wastes are also a problem and are normally treated with the same methods used by refineries.